The invention relates to a deflection unit for use in a color cathode-ray tube of the in-line type having on the display screen a structure of uninterrupted phosphor lines, comprising:
a yoke ring of ferromagnetic material,
a saddle-shaped first deflection winding surrounded by the yoke ring and having a front and a rear end for deflecting, in a first direction, electron beams generated in the cathode-ray tube, the electron beams, when the deflection unit is provided on a cathode-ray tube, passing through the winding in the direction from the rear to the front end;
a second deflection winding likewise having a front and a rear end for deflecting in a direction transverse to the first direction electron beams generated in the cathode-ray tube, all this in such manner that the generally used means for the correction of the dynamic convergence can be omitted.
For some time a color cathode-ray tube has become the vogue in which three electron beams are used in one plane; the type of such a cathode-ray tube is usually referred to as "in-line". For reducing convergence errors of the electron beams, use is generally made of a deflection unit having a frame deflection winding which generates a magnetic field of the cushion-shaped type, and having a line deflection winding which generates a magnetic field of the barrel-shaped type. In particular such a deflection unit may show the combination of a saddle-shaped line deflection winding with a frame deflection winding wound toroidally on the yoke.
However, the use of such a "self converging" deflection unit with a given geometry in cathode-ray tubes of the "in-line" type only results in complete elimination of convergence errors with one given screen format. So either the main geometry (for example the length of the winding) must be varied such that a given deflection unit is self-convergent for a different screen format, or extra correction means must be provided. From a point of view of manufacture, however, it is extraordinarily attractive to provide a deflection unit which is self-convergent with different screen formats without it being necessary for the main dimensions of line and frame deflection windings to be varied and without it being necessary to provide extra correction means.